Security Disclaimer

This is a beta build, and is currently under active development. Please be advised of the following:

• This code currently is not audited by an external security auditor, use it at your own risk.
• The code has not been subjected to thorough review by engineers at the Electric Coin Company.
• We are actively changing the codebase and adding features where/when needed.

zcash_client_sqlite

This library contains APIs that collectively implement a Zcash light client in an SQLite database.

One-time IVKs

With the orchard feature, WalletDb stores derived refund and receive keys and recovers their payments through a durable PIR queue. Ordinary block and transaction scanning uses account keys. Returned payments are authenticated with the specific derived key and credited only after local inclusion and spend checks pass. The spend journal retains nullifiers from recognized wallet transactions so a late recovered note cannot resurrect spent funds.

Enable recovery per account with set_one_time_recovery_enabled. Read bounded work with one_time_recovery, perform network requests without a database lock, and commit through record_one_time_lookup and record_one_time_witness. Rolling filter matches enqueue the same work with record_one_time_filters. Filters only reduce network cost. They do not establish ownership. zakura-pir-client's receiver-wallet feature performs bounded network steps and never owns the wallet database.

Seed recovery stops after four complete empty receive histories. Payments extend the four-index issuance window once mined on the wallet's chain, unpaid holes are recycled, and authenticated funding memos identify refund keys. A funded refund key leaves automatic monitoring once every local operation on it is conclusive, and stays monitored while any is active or inconclusive. One with no local operation, such as a key recovered from its funding memo, leaves seven days of chain time after its funding block. check_one_time_history explicitly checks older addresses, supports an exclusive receive bound, and can be cancelled and resumed. Automatic catch-up skips paid keys whose history is complete, so a repeat payment to a paid address is found automatically only inside the rolling block filter window, and otherwise only by check_one_time_history. Turning discovery off preserves owned funds and permits repair of already-owned receipts after a reorg.

See wallet::one_time_ivk::restore for the queue contract and wallet::one_time_ivk::swap for quote ownership and funding. The zakura-one-time-ivk README describes key derivation and the refund memo.

License

Licensed under either of

• Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.